can: mcp25xxfd: Optimize TEF read by avoiding unnecessary SPI transfers

We have already enough information to know how many tx-messages have
been terminated so that we do not have to query TEF every time if
there is anything pending but we can read the tefs blindly.

This avoids 1 SPI transfer per TEF read.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>